Figure 2.

Early appearance of ³H-thymidine-labeled cells in the developing caudate nucleus (CN) and putamen (P). ³H-thymidine was injected at E24, and the embryo (case KP46) was culled at E34. A,B: Same section processed by Nissl staining (A) and by autoradiography (B). C,D: Adjacent sections, nearby the section shown in A and B, processed for tyrosine hydroxylase (TH) immunostaining (C) and acetylcholinesterase (AChE) staining (D). Many ³H-thymidine-labeled S cells are present in both the caudate nucleus and the putamen, and there are labeled cells in the cell bridges traversing the internal capsule (IC). At this developmental stage, the labeled cells in the caudate nucleus (B) fill the lateral part of the caudate nucleus (arrows delineate medial edge of dense band). This labeled zone reaches farther medially than either the TH-positive (arrows in C) or AChE-positive (arrows in D) part of the caudate nucleus. The arrows in C and D are fiducially placed with respect to each other and delineate the medial-most extent of the AChE staining. Note the zone of sparse cell labeling (example at × in B) in the caudate nucleus between the medial band of dense ³H-thymidine labeling (arrows) and the lateral edge of the nucleus; See Figure 3 for comparable images from in KP-38, labeled at E28 and culled at E35. LV, lateral ventricle; GE, ganglionic eminence; Sp, septum. Scale bars = 0.5 mm in A (applies to A,B) and in C (applies to C,D).